Add a histogram metric tracking for how long audio RTP packets are sent

webrtc/audio/time_interval.cc

Index: webrtc/audio/time_interval.cc
diff --git a/webrtc/audio/time_interval.cc b/webrtc/audio/time_interval.cc
new file mode 100644
index 0000000000000000000000000000000000000000..f156af06c80b68b7206a935bc174812b7fbc124d
--- /dev/null
+++ b/webrtc/audio/time_interval.cc
@@ -0,0 +1,56 @@
+/*
+ *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/audio/time_interval.h"
+#include "webrtc/rtc_base/checks.h"
+#include "webrtc/rtc_base/timeutils.h"
+
+namespace webrtc {
+
+TimeInterval::TimeInterval() = default;
+TimeInterval::~TimeInterval() = default;
+
+void TimeInterval::Extend() {
+  Extend(rtc::TimeMillis());
+}
+
+void TimeInterval::Extend(int64_t time) {
+  if (!interval_) {
+    interval_.emplace(time, time);
+  } else {
+    if (time < interval_->first) {
+      interval_->first = time;
+    }
+    if (time > interval_->last) {
+      interval_->last = time;
+    }
+  }
+}
+
+void TimeInterval::Extend(const TimeInterval& other_interval) {
+  if (!other_interval.Empty()) {
+    Extend(other_interval.interval_->first);
+    Extend(other_interval.interval_->last);
+  }
+}
+
+bool TimeInterval::Empty() const {
+  return !interval_;
+}
+
+int64_t TimeInterval::Length() const {
+  RTC_DCHECK(interval_);
+  return interval_->last - interval_->first;
+}
+
+TimeInterval::Interval::Interval(int64_t first, int64_t last)
+    : first(first), last(last) {}
+
+}  // namespace webrtc